drm/i915: Don't grab crtc mutexes in intel_modeset_gem_init()

commit 7ad228b11ec26a820291c9f5a1168d6176580dc1 upstream.

When the pipe A force quirk is applied the code will attempt to grab
a crtc mutex during intel_modeset_setup_hw_state(). If we're already
holding all crtc mutexes this will obviously deadlock every time.

So instead of using drm_modeset_lock_all() just grab the
mode_config.mutex. This is enough to avoid the unlocked mutex warnings
from certain lower level functions.

The regression was introduced in:

 commit 027476642811f8559cbe00ef6cc54db230e48a20
 Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
 Date:   Mon Dec 2 11:08:06 2013 +0200

    drm/i915: Take modeset locks around intel_modeset_setup_hw_state()

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
[danvet: Add cc: stable since the offending commit has that, too.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 15358ad..54ae96f 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9456,9 +9456,9 @@ void intel_modeset_gem_init(struct drm_device *dev)
 
        intel_setup_overlay(dev);
 
-       drm_modeset_lock_all(dev);
+       mutex_lock(&dev->mode_config.mutex);
        intel_modeset_setup_hw_state(dev, false);
-       drm_modeset_unlock_all(dev);
+       mutex_unlock(&dev->mode_config.mutex);
 }
 
 void intel_modeset_cleanup(struct drm_device *dev)